The present invention relates to one component alkoxy-functional room temperature vulcanizable (RTV) compositions. More particularly, the present invention relates to novel scavengers for chemically combined hydroxy groups usually found in silicone RTV compositions, methods for making such scavenger compounds, and methods for making RTV compositions containing such novel scavenger compounds.
Recently a shelf-stable, fast curing, one component, alkoxy-functional RTV composition was disclosed in the patent of White et al., U.S. Pat. No. 4,395,526, issued July 26, 1983, and assigned to the same assignee as the present invention. Basically White et al. teach that moisture curable, polyalkoxy terminated organopolysiloxane RTV compositions can be made by combining:
(1) a silanol terminated polydiorganosiloxane base polymer, PA0 (2) a crosslinking silane, PA0 (3) an effective amount of certain silane scavengers for chemically combined hydroxy radicals such as methanol, and PA0 (4) an effective amount of a condensation catalyst. PA0 (1) a polydiorganosiloxane base polymer; PA0 (2) an effective amount of condensation catalyst; PA0 (3) a stabilizing amount of scavenger for hydroxy radicals having the formula ##STR6## where R is a substituted or unsubstituted organo group having at least two carbon atoms; R.sup.1 is a hydrolyzable leaving group selected from the group consisting of alkoxy, amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido; R.sup.2 and R.sup.3 are independently selected C.sub.1-13 monovalent substituted or unsubstituted hydrocarbon radicals; R.sup.4 is a hydrolyzable leaving group selected from the group consisting of alkoxy, amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido; x is equal to 1 or 2 and y is equal to 0 to 3; and PA0 (4) optionally, an alkoxy functional crosslinking agent of the formula ##STR7## where R.sup.5 is a C.sub.1-8 aliphatic organic radical selected from alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals, alkylcyano radicals or a C.sub.7-13 aralkyl radical; R.sup.6 is a C.sub.1-13 monovalent substituted or unsubstituted hydrocarbon radical; and b equals 0 or 1. PA0 (1) a polydiorganosiloxane base polymer; PA0 (2) an effective amount of condensation catalyst; PA0 (3) a stabilizing amount of scavenger for hydroxy radicals having the formula ##STR9## where R is a substituted or unsubstituted organo group having at least two carbon atoms; R.sup.1 is a hydrolyzable leaving group selected from the group consisting of alkoxy, amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido; R.sup.2 and R.sup.3 are independently selected C.sub.1-13 monovalent substituted or unsubstituted hydrocarbon radicals; R.sup.4 is a hydrolyzable leaving group selected from the group consisting of alkoxy, amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido; x is equal to 1 or 2 and y is equal to 0 to 3 inclusive; and PA0 (4) optionally, an alkoxy-functional crosslinking agent of the formula ##STR10## where R.sup.5 is a C.sub.1-8 aliphatic organic radical selected from alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals, alkylcyano radicals or a C.sub.7-13 aralkyl radical; R.sup.6 is a C.sub.1-13 monovalent substituted or unsubstituted hydrocarbon radical and b equals 0 or 1. PA0 1,1-dimethoxy-2-(dimethylmethoxysilyl)-2-sila-1-azacyclopentane; PA0 1,1-diethoxy-2-(diethylethoxysilyl)-2-sila-1-azacyclopentane; PA0 1,1-diethoxy-2-(dimethylethoxysilyl)-2-sila-1-azacyclopentane; PA0 1,1-diethoxy-2-(dimethylmethoxysilyl)-1-sila-2-azacyclopentane; PA0 1,ethoxy-1-methoxy-2-(dimethylmethoxysilyl)-1-sila-2-azacyclopentane; PA0 1,1-dimethoxy-2-(methyldimethoxysilyl)-1-sila-2-azacyclopentane. PA0 1,1-dimethoxy-2-(dimethylmethoxysilyl)-1-sila-2-aza-3 cyclopentanone and PA0 1,1-dimethoxy-2-(dimethylmethoxysilyl)-1-sila-2-aza-3 cyclohexanone. PA0 1,1-diethoxy-2(trimethylsilyl)-1-sila-2-azacyclopentane; PA0 1,1-dimethoxy-2-(trimethylsilyl)-1-sila-2-azacyclopentane; PA0 1,1-diethoxy-2-(trimethylsilyl)-1-sila-2-aza-3-cyclopentanone PA0 1,1-dimethoxy-2-(trimethylsilyl)-1-sila-2-aza-3-cyclopentanone; PA0 1,1-dipropenoxy-2-(trimethylsilyl)-1-sila-2 azacyclopentane; PA0 1,1-bis(dimethylaminoxy)-2-trimethylsilyl-1-sila-2-azacyclopentane; PA0 1,1-diethoxy-2-(dimethylvinylsilyl)-1-sila-2-azacyclopentane; PA0 1,1-diethoxy-2-(dimethylpropylsilyl)-1-sila-2-azacyclopentane; PA0 1,1-diethoxy-2-(triethylsilyl)-1-sila-2-azacyclopentane; PA0 1-methyl-1-ethylamino-2-(trimethylsilyl)-1-sila-2-azacyclopentane. PA0 3-(2-aminoethylamino)-propyltrimethoxysilane, PA0 .gamma.-aminopropyltriethoxysilane, PA0 .gamma.-aminopropyltrimethoxysilane, PA0 tris-(trimethoxysilylpropyl)isocyanurate, PA0 .gamma.-glycidoxypropyltrimethoxysilane, PA0 .beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, PA0 vinyltrimethoxysilane, PA0 .gamma.-isocyanatropropyltrimethoxysilane, PA0 .beta.-cyanoethyltrimethoxysilane, PA0 .gamma.-methacryloxypropyltrimethoxysilane and PA0 acetoxypropyltrimethoxysilane.
The scavenger of White et al. can be part of the crosslinking silane or a separate compound and must contain a hydrolyzable functional group selected from the group consisting of amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido.
Shortly after the pioneering invention of White et al. it was discovered that compounds other than those disclosed by White et al. could be utilized as scavengers for chemically combined hydroxy groups or as integrated scavenger-crosslinkers. Dziark in U.S. patent application Ser. No. 349,695, filed Feb. 17, 1982, discloses silicone scavenger compounds for hydroxy functional groups which are silicone-nitrogen compounds selected from the group consisting of:
(A) a silicone-nitrogen compound having the formula ##STR3## where Y is selected from R'" and R".sub.2 N, and (B) a silicone-nitrogen polymer comprising (1) from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula ##STR4## (2) from 0 to 97 mole percent chemically combined structural units represented by the formula ##EQU1## where the silicone atoms of said silicon-nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and an SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and a (R").sub.2 N radical, and where the ratio of the sum of said R'" radicals and said (R").sub.2 N radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, and R" is a member selected from the group consisting of hydrogen, monovalent hydrocarbon radicals and fluoroalkyl radicals, R'" is a member selected from the group consisting of hydrogen, monovalent hydrocarbon radicals and fluoroalkyl radicals, and c is a number equal to 0 to 3 inclusive.
Chung et al. in U.S. patent application, Ser. No. 428,038, filed Sept. 29, 1982, discloses additional silazane scavengers which improve upon those disclosed by Dziark in that they function not only as scavengers for chemically combined hydroxy groups, but as integrated scavenger-crosslinkers.
Additional scavengers for chemically combined hydroxy groups or integrated scavenger-crosslinkers are disclosed in the following U.S. patent applications: Lucas, Ser. No. 464,443, filed Feb. 7, 1983, discloses novel acetamide functional silanes and siloxanes; Chung, Ser. No. 338,518, filed Jan. 11, 1982, discloses silanes having cyclic amide functionality; Mitchell, Ser. No. 462,949, filed Feb. 1, 1983, discloses additional amine functional silanes and Swiger et al., Ser. No. 476,000, filed Mar. 17, 1983, discloses additional silane and siloxane scavengers for RTV compositions. All of the foregoing patent applications and the patent of White et al. are assigned to the same assignee as the present invention and are incorporated by reference into the instant disclosure.
One shortcoming of one-component alkoxy-functional RTV compositions such as those described in Dziark, Ser. No. 349,695, and Chung et al., Ser. No. 428,038, is that they tend to be slightly corrosive towards certain metals such as copper and brass. It is believed that this is due to the low molecular weight amino by-products of the scavenging reaction (NH.sub.3 in the case of scavengers such as hexamethyldisilazane) causing contact and vapor corrosion of the metal substrate. It should be noted that such corrosion is not extreme as it manifests itself primarily in the form of a dark discloloration.
Accordingly, it is desirable to provide scavengers for chemically combined hydroxy groups whose by-product of the scavenging reaction is innocuous towards the metal substrate.